Lower cardiac index levels relate to lower cerebral blood flow in older adults

Objective: To assess cross-sectionally whether lower cardiac index relates to lower resting cerebral blood flow (CBF) and cerebrovascular reactivity (CVR) among older adults. Methods: Vanderbilt Memory & Aging Project participants free of stroke, dementia, and heart failure were studied (n 5 314, age 73 6 7 years, 59% male, 39% with mild cognitive impairment). Cardiac index (liters per minute per meter squared) was quantified from echocardiography. Resting CBF (milliliters per 100 grams per minute) and hypercapnia-induced CVR were quantified from pseudo-continuous arterial spin-labeling MRI. Linear regressions with ordinary least-square estimates related cardiac index to regional CBF, with adjustment for age, education, race/ethnicity, Framingham Stroke Risk Profile score (systolic blood pressure, antihypertensive medication use, diabetes mellitus, current cigarette smoking, left ventricular hypertrophy, prevalent cardiovascular disease [CVD], atrial fibrillation), APOE e4 status, cognitive diagnosis, and regional tissue volume. Results: Lower cardiac index corresponded to lower resting CBF in the left (beta = 2.4, p = 0.001) and right (beta = 2.5, p = 0.001) temporal lobes. Results were similar when participants with prevalent CVD and atrial fibrillation were excluded (left temporal lobe beta = 2.3, p = 0.003; right temporal lobe beta = 2.5, p = 0.003). Cardiac index was unrelated to CBF in other regions assessed (p>0.25) and CVR in all regions (p>0.05). In secondary cardiac index 3 cognitive diagnosis interaction models, cardiac index and CBF associations were present only in cognitively normal participants and affected a majority of regions assessed with effects strongest in the left (p<0.0001) and right (p<0.0001) temporal lobes. Conclusions: Among older adults without stroke, dementia, or heart failure, systemic blood flow correlates with cerebral CBF in the temporal lobe, independently of prevalent CVD, but not CVR.